U.S. patent application number 12/642400 was filed with the patent office on 2010-05-06 for spiral type separation membrane element.
Invention is credited to Shinichi Chikura, Mitsuaki Hirokawa, Satoru Ishihara, Yasuhiro Uda.
Application Number | 20100108593 12/642400 |
Document ID | / |
Family ID | 35056021 |
Filed Date | 2010-05-06 |
United States Patent
Application |
20100108593 |
Kind Code |
A1 |
Chikura; Shinichi ; et
al. |
May 6, 2010 |
SPIRAL TYPE SEPARATION MEMBRANE ELEMENT
Abstract
An object of the invention is to provide a spiral separation
membrane element that can reduce the pressure loss of a feed-side
channel and be much less vulnerable to the problem of inhibition or
blockage of the flow in the feed-side channel. The spiral
separation membrane element includes one or more separation
membranes, one or more feed-side channel components, one or more
permeation-side channel components, and a perforated hollow core
tube around which the separation membranes, the feed-side channel
components and the permeation-side channel components are wrapped,
wherein the feed-side channel component is a net formed by fusion
bonding.
Inventors: |
Chikura; Shinichi; (Osaka,
JP) ; Ishihara; Satoru; (Osaka, JP) ;
Hirokawa; Mitsuaki; (Osaka, JP) ; Uda; Yasuhiro;
(Osaka, JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
35056021 |
Appl. No.: |
12/642400 |
Filed: |
December 18, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10593760 |
Sep 22, 2006 |
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PCT/JP2005/004919 |
Mar 18, 2005 |
|
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12642400 |
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Current U.S.
Class: |
210/321.83 |
Current CPC
Class: |
B01D 63/10 20130101 |
Class at
Publication: |
210/321.83 |
International
Class: |
B01D 63/10 20060101
B01D063/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 26, 2004 |
JP |
2004-092415 |
Claims
1. A spiral separation membrane element, comprising a separation
membrane, a feed-side channel component, a permeation-side channel
component, and a perforated hollow core tube around which the
separation membrane, the feed-side channel component and the
permeation-side channel component are wrapped, wherein the
feed-side channel component has a two-layer structure comprising a
first layer composed of first yarns and a second layer composed of
second yarns, wherein: the first yarns include first repeating
portions oblique to the direction of feed fluid flow; the second
yarns include second repeating portions oblique to the direction of
feed fluid flow; the first yarns and the second yarns are fused and
bonded to form third repeating portions substantially parallel to
the direction of feed fluid flow; and the first yarns and the
second yarns form a hexagonal repeating unit.
2. The spiral separation membrane element according to claim 1,
wherein the third repeating portions have thickness of 0.5 to 1.0
mm.
3. The spiral separation membrane element according to claim 1,
wherein the first yarns and the second yarns are 0.15 to 0.5 mm in
diameter.
4. The spiral separation membrane element according to claim 1,
wherein the first repeating portions and the second repeating
portions have a length of 2 to 5 mm.
5. The spiral separation membrane element according to claim 1,
wherein the hexagonal repeating unit has a parallel part arranged
substantially parallel to the direction of feed fluid flow, and the
parallel part is of 1 to 5 mm in length.
6. The spiral separation membrane element according to claim 1,
wherein the first repeating portions and the second repeating
portions form an angle .alpha. of 60.degree. to 120.
7. The spiral separation membrane element according to claim 6,
wherein the angle .alpha. is about 90.degree..
8. The spiral separation membrane element according to claim 6,
wherein the angle .alpha. is bisected by the direction of feed
fluid flow.
9. The spiral separation membrane element according to claim 1,
wherein each of the first yarns form alternating first repeating
portions and the third repeating portions, and each of the second
yarns form alternating second repeating portions and the third
repeating portions.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a divisional application of U.S. patent application
Ser. No. 10/593,760, filed Sep. 22, 2006, which is the U.S.
National Phase under 35 U.S.C. .sctn.371 of International
Application No. PCT/JP2005/004919, filed Mar. 18, 2005, which
claims priority to the Japanese Patent Application No. 2004-092415,
filed Mar. 26, 2004, and the disclosures of which are herein
incorporated by reference in their entireties.
TECHNICAL FIELD
[0002] The invention relates to a spiral separation membrane
element for separating components dissolved in liquid materials.
More specifically, the invention relates to a spiral separation
membrane element that can reduce the pressure loss of the feed side
in contrast to conventional membrane elements and includes a
feed-side channel component whose structure has a stirring effect
for suppression of concentration polarization on the membrane
surface.
BACKGROUND ART
[0003] Some conventional spiral separation membrane elements are
known to have a structure in which one or more separation
membranes, one or more feed-side channel components and one or more
permeation-side channel components are wrapped around a perforated
hollow core tube. In the case of a reverse osmosis membrane, it has
been reported that if a rhombic type net channel component is used
as a feed-side channel component, the pressure loss can be reduced
(for example, see Japanese Patent Application Laid-Open (JP-A) No.
H11 (1999)-235520, JP-A No. 2000-000437 and JP-A No. 2000-042378
below). For example, such a structure is as shown in FIG. 11.
[0004] In order to reduce the pressure loss of a feed-side channel,
a ladder-type net channel component is also employed that is
composed of warp yarns parallel to the direction of feed fluid flow
and weft yarns interlaced with the warp yarns (for example, see
JP-A No. H05 (1993)-168869 below). This publication pays no
attention to the relationship between the thicknesses or diameters
of the warp and the weft or the relationship between the warp
spacing and the weft spacing or discloses nothing about the
thickness of the warp or the weft.
[0005] In the feed-side channel, however, the resistance to feed
water flow significantly depends on the feed-side channel
component, and the nature of feed water or components contained in
feed water can be a cause of an increase in the resistance
depending on the quality of feed water.
[0006] In the conventional ladder type net, the weft and the warp
are generally the same in diameter, the weft can inhibit the flow
of feed fluid, and suspended components can cause blockage of the
channel. In the rhombic type net with no differentiation between
warp and weft, the yarns in two intersecting directions cross the
flow channel so that the same problem can occur. Namely, there is a
problem in which components suspended in feed fluid can get snagged
on the weft of the feed-side channel component to increase the flow
resistance or block the flow, though the feed-side flow channel
component is required to have not only the function of making the
feed-side pressure loss as small as possible but also the function
of facilitating surface regeneration on the membrane surface and
suppressing concentration polarization. There is also another
problem in which the effective membrane area can be reduced because
components suspended in feed fluid can get snagged on the weft of
the feed-side channel component and be deposited on the membrane
surface. An additional challenge is to reduce the pressure loss of
the feed-side channel component for the purpose of reducing the
running cost of separation membrane elements.
[0007] In many cases, conventional nets are formed by a shear
method such that fusion bonding between the warp and the weft can
be ensured. The shear method uses dies having a number of nozzle
holes that are arranged at two circumferential portions (inner and
outer portions) in an extruder such that when warp and weft yarns
are extruded from the inner and outer nozzle holes being rotated in
opposite directions so as to be fused to each other at
intersections, both nozzle holes overlap one another to form a
single nozzle hole at the intersection of the warp and weft yarns.
In the shear method, the amount of extruded resin becomes high at
the intersections of the warp and weft yarns so that these portions
are deformed into a web-like form. As a result of investigations,
the inventors have found that the web-like form causes an increase
in the pressure loss of the feed-side channel.
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0008] It is therefore an object of the invention to provide a
spiral separation membrane element which can reduce the pressure
loss of the feed-side channel and be much less vulnerable to the
problem of the inhibition or blockage of the flow in the feed-side
channel.
Means for Solving the Problems
[0009] As a result of making active investigations, the inventors
have found that the spiral separation membrane element as described
below can achieve the above object and have completed the
invention.
[0010] The invention is directed to a spiral separation membrane
element, including one or more separation membranes, one or more
feed-side channel components, one or more permeation-side channel
components, and a perforated hollow core tube around which the
separation membranes, the feed-side channel components and the
permeation-side channel components are wrapped, wherein the
feed-side channel component is a net formed by fusion bonding. In
this element, the net formed by fusion bonding has a structure in
which constituent yarns of the net are fused and bonded to each
other to form intersections, and the fused and bonded portions do
not protrude from the constituent yarns in a plane form (a
projection figure).
[0011] The inventors have found that the web-like deformation of
intersections is significantly less in net products formed by a
fusion bonding method than in those formed by the shear method and
that the net products formed by the fusion bonding method can
reduce the pressure loss of the feed-side channel and is effective
in preventing inhibition or blockage of the flow in the feed-side
channel and thus can form excellent spiral separation membrane
elements.
[0012] Advantageously, the products formed by the fusion bonding
method have a relatively smooth surface as compared to the surface
of the products formed by the shear method so that damage to the
membrane by contact with or wrapping and pressing onto the membrane
surface can be lessened in the process of assembling the element,
and thus they are very useful for the production of spiral
separation membrane elements.
[0013] In the feed-side channel component according to the
invention, weft yarns crossing the direction of feed fluid flow are
preferably thinner than warp yarns arranged along the direction of
feed fluid flow. The net products with thinner weft yarns crossing
the direction of feed fluid flow can provide a larger
cross-sectional channel area for feed fluid and thus are effective
against inhibition or blockage of the flow in the feed-side channel
and can reduce the pressure loss of the channel.
[0014] The feed-side channel component is preferably a net channel
component having a structure in which the warp yarns arranged along
the direction of feed fluid flow are meandering. It is known that
generating turbulent fluid flow in a channel is effective in
preventing the inhibition or blockage of the flow in the channel
(turbulence effect). According to the invention, it has been found
that the structure with warp yarns meandering in the channel
component can produce a larger turbulence effect than the
conventional channel component such as the ladder type or the
rhombic type, and thus there can be provided excellent spiral
separation membrane elements with less pressure loss of the
feed-side channel.
[0015] The feed-side channel component preferably has a two-layer
structure including a first layer composed of first yarns and a
second layer composed of second yarns, in which the first and
second yarns each have a parallel part repeated and arranged
substantially parallel to the direction of feed fluid flow and an
oblique part repeated and arranged in a direction oblique to the
direction of feed fluid flow, and the parallel part of the first
yarn and the parallel part of the second yarn are fused and bonded
to form a hexagonal plane unit.
[0016] In this feed-side channel component, the first and second
yarns are overlapping and fused and bonded to each other at the
parallel part, so that this part can be less resistant to feed
fluid, and the hexagonal plane unit can reduce the number of the
intersections per unit flow length (the number of the parallel
parts in this case) so that the pressure loss of the feed-side
channel can be further reduced.
[0017] Alternatively, the feed-side channel component preferably
has a three-layer structure including warp yarns arranged
substantially parallel to the direction of feed fluid flow, oblique
yarns arranged in a direction oblique to the direction of feed
fluid flow, and reverse oblique yarns arranged in a direction that
is reversely oblique to the direction of feed fluid flow with
respect to the direction of the oblique yarns.
[0018] In such a feed-side channel component, the layer composed of
the warp yarns can be less resistant to feed fluid, and the part
composed of the reverse oblique yarns and oblique yarns (thinner
than those in the case of the two-layer structure) crossing the
direction of feed fluid flow can also be less resistant to feed
fluid, so that the pressure loss of the feed-side channel can be
further reduced.
EFFECTS OF THE INVENTION
[0019] As described above, the fusion bonding method is used to
form the net for use in the spiral separation membrane element
according to the invention so that there is provided an advantage
in that the pressure loss of the feed-side channel can be reduced
and the inhibition or blockage of the flow can be prevented in the
feed-side channel. There is also provided an advantage in that
workability can be high in the process of assembling the element or
other processes.
[0020] In addition, if thinner weft yarns are used which cross the
direction of feed fluid flow, if any one-directional set of yarns
are thinner than the other directional set of yarns in the rhombic
type net channel component, or if the ladder type net channel
component has a structure with meandering warp yarns, the pressure
loss of the feed-side channel can be further reduced, or the
inhibition or blockage of the flow can be effectively prevented in
the feed-side channel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a schematic diagram showing a net type according
to an embodiment of the invention (first structural example);
[0022] FIG. 2 is a schematic diagram showing a net type according
to another embodiment of the invention (second structural
example);
[0023] FIG. 3 is a schematic diagram showing a net type according
to a third embodiment of the invention (third structural
example);
[0024] FIG. 4 is a schematic diagram showing a net type according
to a fourth embodiment of the invention (fourth structural
example);
[0025] FIG. 5 is a schematic diagram showing another net type
according to the fourth embodiment of the invention (fourth
structural example);
[0026] FIG. 6 is a schematic diagram showing a net type according
to a fifth embodiment of the invention (fifth structural
example);
[0027] FIG. 7 is a schematic diagram illustrating the relationship
between the flow rate of feed fluid and the pressure loss in
Example 1 according to the invention;
[0028] FIG. 8 is a schematic diagram illustrating the relationship
between the flow rate of feed fluid and the pressure loss in
Example 2 according to the invention;
[0029] FIG. 9 is a schematic diagram showing a comparison between
pressure losses in Example 3 according to the invention;
[0030] FIG. 10 is a schematic diagram showing a comparison between
pressure losses in Example 4 according to the invention; and
[0031] FIG. 11 is a schematic diagram showing a rhombic type net in
a conventional mode.
DESCRIPTION OF THE NUMERALS
[0032] 1 Warp yarns [0033] 2 Weft yarns [0034] 3 Thickness [0035] 4
Warp spacing [0036] 5 Weft spacing [0037] 6 Crossing angle [0038] 7
Meandering warp angle [0039] 11 First yarns [0040] 11a Parallel
part of the first yarn [0041] 11b Oblique part of the first yarn
[0042] 12 Second yarns [0043] 12a Parallel part of the second yarn
[0044] 12b Oblique part of the second yarn [0045] 15 Oblique yarns
[0046] 16 Warp yarns [0047] 17 Reverse oblique yarns
BEST MODE FOR CARRYING OUT THE INVENTION
[0048] Some embodiments of the invention will be described below
with reference to the drawings. In FIG. 1, Parts (A) and (B) are
front and side views, respectively, showing an example of the
feed-side channel component of the spiral separation membrane
element according to the invention.
[0049] The spiral separation membrane element of the invention has
a structure in which one or more separation membranes, one or more
feed-side channel components and one or more permeation-side
channel components are wrapped around a perforated hollow core
tube. Such a structure of a membrane element is also described in
detail in Patent Japanese Patent Application Laid-Open (JP-A) No.
H11 (1999)-235520, JP-A No. 2000-000437, JP-A No. 2000-042378 and
JP-A No. H05 (1993)-168869 above, and except for the feed-side
channel component, the separation membrane, permeation-side channel
component or perforated hollow core tube may be any conventionally
known one. For example, in a case where a plurality of feed-side
channel components and a plurality of permeation-side channel
components are used, the structure includes a plurality of membrane
leaves wrapped around the hollow core tube.
[0050] Referring to FIG. 1, for example, the feed-side channel
component for use in the invention is a ladder type net channel
component having warp yarns 1 and weft yarns 2 with respect to the
direction of feed fluid flow as shown in the drawing. The invention
is characterized in that the feed-side channel component is a net
formed by a fusion bonding method.
[0051] The fusion bonding method for forming the net generally
includes the steps of extruding weft and warp yarns from a number
of nozzle holes arranged at two circumferential portions (inner and
outer portions) of dies in an extruder while rotating the inner and
outer nozzle holes in opposite directions, fusing and bonding the
weft and warp yarns to each other to form intersections, dipping
them into a cooling bath, and then taking out them. In the process
of performing the extrusion, the nozzle holes are arranged such
that both nozzle holes do not overlap one another at the
intersections of the weft and warp yarns (this feature differs from
the shear method), and the extruded weft and warp yarns are fused
and bonded to each other with appropriate timing of fusion
bonding.
[0052] As compared with the shear method, therefore, the shapes of
the weft and warp yarns can easily be maintained at the
intersections with no increase in the amount of extruded resin at
the intersections so that the web-like deformation can be
remarkably reduced and that the pressure loss of the feed-side
channel can be reduced.
[0053] Particularly in the process of forming the net as shown in
Part (A) of FIG. 1 by the fusion bonding method, it is effective to
use a method in which the nozzle diameter for the weft yarns
differs from that for the warp yarns, and only the nozzle holes for
the weft yarns are rotated without rotating the nozzle holes for
the warp yarns.
[0054] Materials selected in view of corrosion resistance, heat
resistance, mechanical strength or the like (as described later)
are a structural factor of the channel component. Besides the
materials, the cross-section area of the channel is also an
important structural factor. In the structural example as shown in
Part (A) of FIG. 1, examples of the structural factor include the
diameter of the warp yarn 1, the diameter of the weft yarn 2, the
thickness 3 depending on the diameters, the warp spacing 4, the
weft spacing 5, and the crossing angle 6. In view of mechanical
strength, for example, the diameters of the warp and weft yarns 1
and 2 may preferably be as large as possible. However, such large
diameters lead to a reduction in the cross-section area of the
channel and to an increase in the pressure loss and thus are not
preferred. In view of strength, small crossing angles are
preferred, because such small angles provide a large bonded area
between the warp and weft yarns 1 and 2. However, such small angles
can lead to a reduction in the warp spacing 4 or in the
cross-section area of the channel and to an increase in the
pressure loss and thus are not preferred.
[0055] The inventors have selected these factors to form a channel
that is optimum for a reduction in the pressure loss of the channel
or for the prevention of inhibition or blockage of the flow and
investigated the effect of the detailed structure and state of the
intersections of the warp and weft yarns 1 and 2. As a result, the
inventors have found that the fusion bonding method is optimum for
allowing smooth flow without web-like deformation or the like.
[0056] Specifically, while the intersections of the net produced by
the conventional method such as the shear method are deformed into
a web-like form, such a deformation is remarkably less in the
product formed by the fusion bonding method according to the
invention than in the product formed by the shear method.
Advantageously, the product formed by the fusion bonding method
have a relatively smooth surface as compared to the surface of any
other product such as the product formed by the shear method, so
that damage to the membrane by contact with or wrapping and
pressing onto the membrane surface can be lessened in the process
of assembling the element. Such an advantage is very useful in
forming the channel component, and the product formed by the fusion
bonding method according to the invention can form a new excellent
spiral separation membrane element even with a similar structure to
that of the conventional product.
[0057] Particularly in the ladder type channel component, the weft
yarns 2 to be brought into contact with the flow is made longer in
many cases, and thus such an advantage of the product formed by the
fusion bonding method can be fully utilized so that the superiority
of the ladder type channel component itself and the advantage of
the product formed by the fusion bonding method can synergistically
be utilized.
[0058] While any material may be used to form the raw water-side
channel component of the feed-side channel, the material is
selected in view of corrosion resistance, heat resistance,
mechanical strength or the like as mentioned above. Examples of
such a material include polypropylene and polyethylene.
[0059] In order to reduce the pressure loss for feed fluid flow,
the weft yarns crossing the direction of feed fluid flow may be
made relatively thin as shown in Part (B) of FIG. 1 so that the
cross-section area of the feed fluid channel can be made relatively
large. Such a structure is effective against the inhibition or
blockage of the flow in the feed-side channel and can reduce the
pressure loss of the channel.
[0060] Specifically, the conventional ladder type channel component
is composed of weft and warp yarns with substantially the same
diameter, and its actual cross-sectional channel area is less than
half of the cross-section area of the raw water side of the
feed-side channel. This applies to the case of the rhombic type
channel component. In the channel component according to the
invention, the ratio of the diameter of the weft yarn to that of
the warp yarn (for the ladder type) or the ratio of the diameter of
the yarn in one direction to that in the other direction (for the
rhombic type) may be set low so that the cross-section area of the
channel can be set large and that the pressure loss can be smaller
than that of the conventional product. Specifically, the inventors
have found that the ratio of the diameter of the warp yarn to that
of the weft yarn (warp:weft) is properly from 4:1 to 2:1. Using
such a structure in the product formed by the fusion bonding method
according to the invention ensures remarkably little web-like
deformation of intersections as compared with the conventional
product formed by the shear method or the like, ensures the effect
of the reduction in the ratio of the diameter of the weft to that
of the warp, and produces a factor for a further reduction in flow
resistance.
[0061] In addition to the increase in the cross-section area of the
channel, the entire surface of the weft yarns 2 can be in contact
with the flow according to the invention. Therefore, there can be
produced an synergistic effect in which the surface smoothness of
the product formed by the fusion bonding method or the function of
lessening the damage to the membrane by contact with or wrapping
and pressing onto the membrane surface in the process of assembling
the element can be further enhanced by the reduction in the
diameter of the weft yarns 2, so that there can be provided an
excellent spiral separation membrane element with much less
pressure loss of the feed-side channel.
[0062] FIG. 2 shows the structure of a modified ladder type net
channel component that forms another type of the spiral separation
membrane element according to another embodiment of the invention
(second structural example). In this structure, the warp yarn 1 is
shifted in the direction of feed fluid flow such that the crossing
angle 6 increases. In this structure, therefore, the warp spacing 4
is increased while the joint between the warp and weft yarns 1 and
2 are retained. This structure can increase the length of the joint
between the warp and weft yarns 1 and 2 and ensure a sufficient
strength of the net channel component and form an excellent net
capable of having a relatively large cross-sectional channel
area.
[0063] This structure also has a new excellent function in that the
pressure loss can be controlled by adjusting the crossing angle 6
in the channel. Specifically, the warp spacing 4 and the
cross-sectional channel area increase as the crossing angle 6
increases as described above, while the warp spacing 4 and the
cross-sectional channel area decrease as the crossing angle 6
decreases. As the crossing angle 6 increases however, the weft
spacing 5 decreases so that the pressure loss can increase. In this
case, the pressure loss-reducing effect by the increase in the
cross-sectional channel area can be restricted. Thus, the warp
spacing 4, the weft spacing 5 and the crossing angle 6 are properly
selected so that a channel component with the desired pressure loss
can be prepared.
[0064] FIG. 3 shows a third structural example according to the
invention, which is a ladder type net channel component
characterized in that the warp yarns are in the form of a
meandering structure. Bringing the flow in the channel into a
turbulent state is effective in preventing the inhibition or
blockage of the flow in the channel and in reducing the pressure
loss. The meandering structure of the warp yarns of the channel
component can produce a larger turbulence effect than the
conventional ladder or rhombic type channel component. Thus, there
can be provided an excellent spiral separation membrane element
with less pressure loss of the feed-side channel. Particularly in a
case where the warp and the weft are different in diameter, this
structure can enhance the turbulence of the flow and produce an
increased turbulence effect so that the pressure loss of the
feed-side channel can be further reduced.
[0065] In the conventional ladder type, the turbulence effect is
produced by the weft, while in the rhombic type with no
differentiation between warp and weft, the turbulence effect is
produced by the two-directional crossing yarns. In the channel
component according to the invention, the meandering structure of
the warp yarns has easily produced a turbulence effect higher than
that produced by linear warp yarns parallel to the water flow. In
this structure of the channel component, a new factor, the
meandering warp angle 7 as shown in FIG. 3, is added to the
structural factors of the first structural example according to the
invention, such as the diameter of the warp yarn 1, so that optimum
channel conditions can be set to reduce the pressure loss of the
channel or to prevent the inhibition or blockage of the flow. Like
the case of the second structural example, the warp spacing 4, the
weft spacing 5, the crossing angle 6, and the meandering warp angle
7 are properly selected so that a channel component with the
desired pressure loss can be prepared.
[0066] Specifically, a study has been performed on a raw water-side
channel component with a provisionally specified thickness of 26
mil, 28 mil or 34 mil for use in the feed-side channel. The result
of the study indicates that the structural factor of the feed-side
channel should preferably be set in the range as shown in Table 1
in order to produce the effect of reducing the pressure loss to 1/2
of the conventional product level.
TABLE-US-00001 TABLE 1 Unit 26 mil 28 mil 34 mil Factors (mm) (0.64
to 0.68) (0.69 to 0.73) (0.84 to 0.88) Warp Diameter mm 0.44 to
0.49 0.47 to 0.53 0.57 to 0.65 Weft Diameter mm 0.17 to 0.22 0.18
to 0.24 0.21 to 0.29 Diameter Ratio -- The ratio of warp diameter
to thickness is 67 to of Warp 75% (warp:weft = 4:1 to 2:1). to Weft
Warp Spacing mm 3 to 5 Weft Spacing mm 3 to 10 Spacing Ratio -- 2:1
to 1:1 of Warp to Weft Weft Angle .degree. 45 to 90 Meandering
.degree. 0 to 30 Warp Angle
[0067] With respect to the formation of the channel component, the
above three structural examples according to the invention can be
prepared by forming a specific channel component and then changing
the degree of expansion or contraction in its width direction (a
direction perpendicular to the direction of feed water flow) in the
order of the first, second and third structural examples. Thus,
these channel components have an excellent feature in that they can
be very easily prepared depending on use conditions.
[0068] FIGS. 4 and 5 show a fourth structural example according to
the invention, in which Part (A) is a front view, Part (B) a side
view, and Part (C) a bottom view. In this example, referring to
FIGS. 4 and 5, the feed-side channel component has a two-layer
structure including a first layer L1 composed of first yarns 11 and
a second layer L2 composed of second yarns 12. In this structure,
the first and second yarns 11 and 12 each have a parallel part 11a
or 12a repeated and arranged substantially parallel to the
direction of feed fluid flow and an oblique part 11b or 12b
repeated and arranged in a direction oblique to the direction of
feed fluid flow. In addition, the parallel part 11a of the first
yarn 11 and the parallel part 12a of the second yarn 12 are fused
and bonded to form a hexagonal plane unit.
[0069] In the fourth structural example as shown in FIG. 4, the
respective oblique parts 11b and 12b of the first and second yarns
11 and 12 are inclined in the same direction. In the fourth
structural example as shown in FIG. 5, the respective oblique parts
11b and 12b of the first and second yarns 11 and 12 are inclined in
opposite directions. In the structure as shown in FIG. 5, the first
and second yarns 11 and 12 are each arranged in a meandering manner
along the direction of feed fluid flow so that the pressure loss of
the feed-side channel can be further reduced.
[0070] In the process of forming the net as shown in FIG. 4 by the
fusion bonding method, nozzle holes for the first yarns 11 and
nozzle holes for the second yarns 12 may be intermittently rotated
in opposite directions by performing a control in such a manner
that the rotation of both nozzles is stopped only when the parallel
parts 11a and 12a are extruded. In such a process, the extruded
parallel parts 11a and 12a are fused and bonded to each other.
[0071] The process of forming the net as shown in FIG. 5 by the
fusion bonding method may include the steps of extruding the
oblique parts 11b and 12b while rotating both nozzle holes in
opposite directions, extruding the parallel parts 11a and 12a while
stopping the rotation of both nozzle holes, extruding next oblique
parts 11b and 12b while rotating each of the nozzle holes in a
direction opposite to the direction for the previous extrusion of
the oblique parts 11b and 12b, then stopping the rotation of both
nozzle holes, and repeating the above steps.
[0072] In this structural example, the intersections of the first
and second yarns 11 and 12 are preferably 0.5 to 1.0 mm in
thickness. The first and second yarns 11 and 12 are also preferably
0.15 to 0.5 mm in diameter. Preferably, the hexagonal plane unit
has an apex angle .alpha. of 60.degree. to 120.degree., an oblique
side length A or B (that is the length of the oblique part 11b or
12b) of 2 to 5 mm, and a parallel part 11a or 12a length of 1 to 5
mm.
[0073] FIG. 6 shows a fifth structural example according to the
invention, in which Part (A) is a front view, Part (B) a side view,
and Part (C) a bottom view. Referring to FIG. 6, this example has a
three-layer structure including first, second and third layers L1,
L2 and L3. Each layer is composed of warp yarns 16 arranged
substantially parallel to the direction of feed fluid flow, oblique
yarns 15 arranged in a direction oblique to the direction of feed
fluid flow, and reverse oblique yarns 17 arranged in a direction
that is reversely oblique to the direction of feed fluid flow with
respect to the direction of the oblique yarns 15.
[0074] In the process of forming the net as shown in FIG. 6 by the
fusion bonding method, the warp yarn 16, the oblique yarn 15 and
the reverse oblique yarn 17 may be fused and bonded to one another
to form intersections with the nozzle hole for the warp yarn 16 not
rotating and with the nozzle holes for the oblique yarn 15 and the
reverse oblique yarn 17 rotating in opposite directions.
[0075] The warp yarns 16, the oblique yarns 15 and the reverse
oblique yarns 17 may be stacked in any order. Particularly, if the
second layer L2 is composed of the warp yarns 16, the flow
resistance can be low in the intermediate layer so that the
pressure loss of the feed-side channel can be further reduced. In
this case, concentration polarization can also be effectively
suppressed in the vicinity of the membrane surface by a turbulence
effect, because the oblique yarns 15 and the reverse oblique yarns
17 are in contact with the membrane surface.
[0076] The intersection of the first layer L1 and the second layer
L2 may not coincide with that of the second layer L2 and the third
layer L3. In terms of improving the morphological stability of the
feed-side channel component, both intersections preferably coincide
with each other.
[0077] In the fifth structural example, the intersections of the
warp yarns 16, the oblique yarns 15 and the reverse oblique yarns
17 are preferably 0.5 to 1.0 mm in thickness. The warp yarns 16,
the oblique yarns 15 and the reverse oblique yarns 17 are also
preferably 0.1 to 0.5 mm in diameter. The plane unit form
preferably has an oblique side length D of 2 to 5 mm. The angle
.alpha. between the oblique yarn 15 and the reverse oblique yarn 17
is preferably from 60.degree. to 120.degree..
[0078] The diameters of the warp yarn 16, the oblique yarn 15 and
the reverse oblique yarn 17 may be the same or different. If the
warp yarns 16 forming the second layer L2 are relatively thick, the
pressure loss of the feed-side channel can be further reduced. In
contrast, if the warp yarns 16 forming the second layer L2 are
relatively thin, concentration polarization can be effectively
suppressed in the vicinity of the membrane surface by a turbulence
effect.
EXAMPLES
[0079] The structure and effects of the invention are specifically
described with reference to the examples and the like below. It
will be understood that the examples do not limit the scope of the
invention.
Example 1
Comparative Example 1
[0080] The feed-side channel component as shown in Table 2 was
placed in a parallel plate cell (C10-T, 35 mm in channel width, 135
mm in channel length). FIG. 7 shows the flow rate and the pressure
loss at the time when purified water was allowed to flow into the
channel component. The nets of Example 1 and Comparative Example 1
differ in the forming method and in the weft diameter, while the
other specifications of the nets are the same. Nevertheless, the
pressure loss in Example 1 was about 1/3 of that in Comparative
Example 1.
TABLE-US-00002 TABLE 2 Comparative Factors Unit Example 1 Example 1
Forming Method -- Fusion Bonding Shear Method Net Type -- Ladder
Type Ladder Type Overall Thickness mm 0.71 0.71 Weft Diameter mm
0.18 0.4 Warp Spacing mm 3.4 3.5 Weft Spacing mm 3.9 4.1 Crossing
Angle .degree. 48 48 Meandering Warp Angle .degree. 0 0
Example 2
Comparative Example 2
[0081] A 23.2 m.sup.2 spiral element was prepared using the
feed-side channel component as shown in Table 3 and then loaded in
a pressure vessel. FIG. 8 shows the flow rate and the pressure loss
at the time when purified water was allowed to flow into the
element loaded in the pressure vessel. The pressure loss in Example
2 was at most about 2/3 of that in Comparative Example 2.
TABLE-US-00003 TABLE 3 Comparative Factors Unit Example 2 Example 2
Forming Method -- Fusion Bonding Shear Method Net Type -- Ladder
Type Rhombic Type Overall Thickness mm 0.85 0.86 Weft Diameter mm
0.24 0.46 Warp Spacing mm 4.0 3.2 Weft Spacing mm 3.6 3.2 Crossing
Angle .degree. 60 89 Meandering Warp Angle .degree. 25 --
[0082] The performance of each of the spiral elements of Example 2
and Comparative Example 2 was examined with respect to NaCl. As a
result, it has been demonstrated that the blocking performance of
Example 2 is not lower than that of Comparative Example 2 and that
a turbulence effect is sufficiently obtained to maintain the
concentration polarization in Example 2, as shown in Table 4.
TABLE-US-00004 TABLE 4 Comparative Items Unit Example 2 Example 2
NaCl Blocking Performance % 99.46 99.35 Water Permeable Flow
m.sup.3/d 35.53 35.48
Example 3
Comparative Example 3
[0083] The feed-side channel component as shown in Table 5 was
placed in a parallel plate cell (C10-T, 35 mm in channel width, 135
mm in channel length). FIG. 9 shows the pressure loss at the time
when purified water was allowed to flow into the channel component
at an average flow rate of 0.2 m/second. The nets of Example 3 and
Comparative Example 3 differ in the forming method and in the plane
unit form, while the other specifications of the nets are the same.
Nevertheless, the pressure loss in Example 3 was about 60% of that
in Comparative Example 3.
TABLE-US-00005 TABLE 5 Comparative Items Unit Example 3 Example 3
Forming Method -- Fusion Bonding Fusion Bonding Net Type --
Hexagonal Type (FIG. 4) Rhombic Type Overall Thickness mm 0.71 0.71
Yarn Diameter mm 0.36 0.36 Yarn Spacing mm -- 3 Size A or B mm 3 --
Size C mm 2 -- Apex Angle .degree. 90 90
Example 4
Comparative Example 4
[0084] The feed-side channel component as shown in Table 6 was
placed in a parallel plate cell (C10-T, 35 mm in channel width, 135
mm in channel length). FIG. 10 shows the pressure loss at the time
when purified water was allowed to flow into the channel component
at an average flow rate of 0.2 m/second. The nets of Example 4 and
Comparative Example 4 differ in the forming method and in the plane
unit form, while the other specifications of the nets are the same.
Nevertheless, the pressure loss in Example 4 was about 60% of that
in Comparative Example 4.
TABLE-US-00006 TABLE 6 Items Unit Example 4 Comparative Example 4
Forming Method -- Fusion Bonding Fusion Bonding Net Type --
Three-Layer Type Rhombic Type Overall Thickness mm 0.71 0.71 Yarn
Diameter mm 0.25 0.36 Size D mm 3 3 Apex Angle .degree. 90 90
INDUSTRIAL APPLICABILITY
[0085] While the feed-side channel component may be used in any
application, it is effectively used in separation membrane elements
or in low pressure elements to generally treat suspended
matter-containing waste water (raw water) or the like.
* * * * *